In normal-weight subjects, the effects of a high carbohydrate (hi-cho) vs high fat (hi-fat) diet/meal on lipoprotein lipase (LPL) responsiveness in adipose tissue (AT) or skeletal muscle (SM) will predict weight stability vs weight gain over 5 yr and in obese subjects, the effects of a hi-cho vs hi-fat diet/ meal on tissue-specific LPL responsiveness will predict weight stability of the obese weight vs additional weight gain over 5 yr.